Let off (fwd)

[Charles K. Ball]

>To the list:
>
>I've long felt that let-off is one of the most important things we deal
>with in regulating grands (or even verticals).  I always try in the
>treble to get the closest let-off possible short of having a double
>bounce effect.  In the mid-range one needs to consider the string ampli-
>tude and make it a little wider so that when the string is in its down-
>ward excursion the jack isn't jammed tight when the hammer contacts
>the string causing a nasty twang.  The same thing is true in the Bass,
>except more so.
>
>The problem that I face often is that, since I usually do the voicing
>last, if I have to do any deep shoulder voicing in the treble, it causes
>the hammers to lengthen slightly so that the hammers will block on a
>pianissimo blow using a soft stiff fingered attack.  Then I have to go
>back over the let-off to correct that and then recheck after-touch etc.
>
>I would like to know some of the experiences of others in regard to this.
>
>Jim Coleman, Sr. (AZ)  (who still doesn't know it all.)


Dear Jim,

I agree about the importance let-off, especially for responsiveness in very
soft playing--if the let-off is too wide, the hammer simply may not speak
if the key is played slowly.  On grands I do the let-off in the piano,
using both my eyes and ears.

In the course of an action reconditioning I will make several passes, as
many subsequent adjustments and movements may affect let-off, i.e. hammer
spacing, whippen spacing, key frame bedding, etc.  Also, the method of
checking hammer fitting in which one presses the hammer to the string with
the jack, forcing the jack tender against the let-off punching, may move
the let-off closer.

In general, after the first pass, however, the subsequent passes go quite
quickly.  Bill Garlick teaches an aural method of fine tuning let-off which
he terms "ghosting", a term borrowed from harpsichord terminology.  It is
best demonstrated, but I will attempt a description.  First visually set
the let-off as close as practical--this should take only 20 to 30 minutes.
Then (my interpolation), in order to obtain stability, press down groups of
keys, starting in the bass, with the heal of one hand, while shoving the
corresponding jack tenders firmly into their punchings to settle the
compaction quickly.  Proceed throughout the keyboard.  This should take
less than five minutes.

Next raise the dampers with the damper pedal, and, starting with note #1,
press each note slowly enough that under normal circumstances it will not
speak, but do so with a decisive, firm motion (this is where it is best to
demonstrate).  Actually you first push the key down to the let-off point,
so that there is little momentum, and then "click" it on through let-off.
If you find it impossible to keep the hammer from speaking, then you need
to screw down the let-off button a tad.  This may take an additional ten or
fifteen minutes.

I hope that I am doing justice to Bill's procedure, but once you get the
hang of this "tripping" or "clicking" of the hammer through escapement and
achieve absolute consistency, you will be able to produce a very close, but
accurate let-off that will be unlikely to produce bobbling (until the
humidity goes up!).  Bill warns that this method has its hazards, and
should be reserved for the professional instrument that receives frequent
service.  This is also a helpful method for those hammers that are
difficult to see clearly because of the dampers (usually in the bass) or
the capo bar.  It can work well, with some modification,  for the visually
impared technician.

When setting let-off this closely, there is no way that I can see to avoid
frequent checking; but using the "ghosting" method this goes really
quickly.

Regards,

Charles

Charles Ball, RPT
School of Music
University of Texas at Austin
ckball@mail.utexas.edu